Study on the precursory characteristics and influencing factors of rockburst in the bifurcation area of coal seam.

To explore the precursory characteristics and influencing factors of rockburst in the bifurcation area of coal seam, the evolution and expansion of fracture and the energy accumulation and dissipation characteristics of coal-rock parting-coal structure (CRCS) during failure and instability process are explored from a micro-scopic perspective, and the influence of coal and rock parting parameters on the instability is studied. The following four points are addressed: (1) Compared with the single coal structure or the coal- rock combined structure, the CRCS can more directly reflect the geological structure characteristics of the coal seam in the bifurcated area; (2) The failure and instability process of CRCS includes two types of instability: slip and fracture. The slip instability is characterized by low strength and high energy release, which is very difficult to predict. (3) Before the failure of CRCS, there are several precursor signal characteristics, such as the shortened development time of the "stable-fracture-stable" cycle, abnormal slip dislocation of the contact surface, and rapid accumulation of rock fracture energy. (4) The inclination angle of the contact surface affects the instability form, the strength of the rock parting affects the instability state, and the thickness of the rock parting affects the impact tendency. The research results have important theoretical significance for preventing rockburst caused by failure and instability in bifurcated area of coal seam.